The invention relates to a process for the production of artificial tobacco and an apparatus for performing this process.
It is known to produce artificial tobacco by shaping and drying a moist paste of plant parts, binders, adsorbents, further chemicals and liquid. In order to ensure that the chemicals are distributed as uniformly as possible in the paste, the latter must contain more liquid than is necessary for further processing. The resultant paste has been hitherto shaped into for example sheets, fibres, strips, foils and the like, and then the liquid contained, other than a residual quantity, removed by evaporation. This procedure requires substantial energy to remove the excess liquid and it is an object of the present invention to reduce this amount of energy.
The process according to the invention is characterised in that the paste is mixed at a 30 to 40% by weight liquid content, is then predried to a 15 to 25% by weight liquid content by pressing out liquid and then shaped and hardened by drying to a 6 to 18% by weight liquid content to form artificial tobacco. The paste is initially mixed with the liquid content desirable for a homogeneous distribution of the chemicals and that portion of the liquid content which is not necessary for shaping is removed by simply squeezing out, so that the shaped sheets etc. are drier from the outset and subsequently require only a relatively small drying energy for the final drying process.
The liquid to be pressed out is generally mainly water, but it is not pure water which is removed from the paste. The pressed out liquid contains dissolved chemical constituents as well as vegetable matter. However, this is not disadvantageous because the substances removed from the paste in this way can be added to a subsequent charge. The liquid obtained during squeezing out can be added directly to a paste which is to be subsequently mixed, or alternatively can be cleaned before such addition.
Experience has shown that a high proportion of albumins is disadvantageous for the smoking flavour of artificial tobacco. It is never possible to completely avoid such albumins, because they are present in almost all plant parts. However, the albumin content can be reduced by subjecting the liquid obtained during squeezing to an albumin separation process during which at least the larger proportion of the albumins contained are separated.
The smoking flavour and burning characteristics of the artificial tobacco are also impaired by various anions. Therefore, when cleaning the liquid, it is recommended to separate chlorides and/or nitrate ions therefrom by ion exchange. Thus, the invention makes it possible to clean the starting material for the artificial tobacco, i.e. the moist paste, and this can take place in a very simple manner, because the cleaning measures are performed on the pressed out liquid.
It is desirable to prevent added chemicals being lost with the pressed out liquid or during the cleaning thereof and account is taken of this in a further embodiment of the invention which is characterised in that at least a proportion of the binders, adsorbents and further chemicals is only added to the paste after the said predrying thereof.
It is desirable for the process of the invention to be performed on a continuous basis and a suitable apparatus for this purpose comprises
a screw conveyor which is mounted coaxially in a circular cylindrical casing;
a charging hopper at the upstream end of the casing;
a liquid drain at the downstream end of the casing, the screw conveyor being so constructed as to have an increasing compressing action on the material conveyed in the conveying direction; and
the downstream end wall of the casing being foraminous.
It is recommended that a heating device be provided for heating the casing and/or the foraminous wall in order to increase the flowability of the predried paste in the kneading and compressing device.
These and further objects, features and advantages of the present invention will become apparent upon perusal of the following description when taken in connection with the accompanying drawings which show for purposes of illustration only several embodiments of the present invention.